The present invention relates to reclosable plastic bags. More specifically, the present invention relates to a method of producing plastic bags which are concurrently manufactured to include a fastener strip and the manner of producing such bags so that the ends of the fastener strip are fused, thereby providing end seals to the fastener strip prior to the fastener strip being attached to the thermoplastic film used to produce the plastic bag.
The present invention relates to improvements in the package making art and may be practiced in the manufacture of reclosable thermoplastic bags and packages of the kind that may be used for various consumer products. Such packages often include a form of peel-seal to render the pack moisture and/or airtight prior to the initial opening and/or a tamper-evident seal. A zipper means protects any remainder of the product therein after the initial opening.
The indicated art is fairly well developed but nevertheless remains open to improvements contributing to increased efficiency and cost-effectiveness. In the prior art, McMahon et al. (U.S. Pat. No. 4,909,017) discloses a method of making a form-fill bag having a reclosable fastener. Prior to entering the form-fill and seal machine, fastener strips are attached to the surface of the film transverse to the running direction at bag length intervals. The fastener strips contain pre-joined interlocked rib and groove strips and only one of the strips is attached to a top surface of the film with the other strip facing upwardly, or, in other words, inwardly toward the interior of the bag to be formed. The attached strips are secured at the center of the film and each strip is less than half of the film width. The film is then advanced to the form-fill and seal machine and drawn down over a forming collar and about the filling tube with the longitudinal side edge margins of the film brought together and seamed with a fin seal to form a tube. Cross seals are made across the tube to join the unattached fastener strip to form the closure and bottom of the bags.
A problem that is sometimes encountered by consumers when they open such bags is that the two zipper halves become separated at the zipper segment ends. This separation of the zipper halves makes it difficult for the consumers to align the zipper profiles to enable the bag to be reclosed. An improvement in the above method would be the ability to make end seals on the fastener strips prior to the attachment of the fastener strips on the thermoplastic film used to make the reclosable bag. The end seals serve to reinforce the ends of the zipper, thereby keeping the profiles aligned.
Accordingly, the present invention relates to an apparatus and method for producing end seals on a continuous supply of fastener strip having first and second interlocking profiles before the fastener strip is attached to a supply of thermoplastic film used to make a reclosable bag. In the method, the continuous supply of fastener strip is fed to and advanced through a guide. A first section of the continuous supply of fastener strip is identified and fused, thereby providing a first end seal. A second end section of the continuous supply of fastener strip is identified based on a measurement from the first end section. The second section is fused, thereby providing a second end seal with the result of a length of fastener strip including a pair of end seals. Prior to entering the bag making machine, the length of fastener strip is separated from the continuous supply fastener strip. The length of fastener strip is then attached to the surface of the thermoplastic film used to make the reclosable bag. In a second embodiment, the first and second sections are fused and simultaneously separated by a cutting device at the exiting end of the fastener guide.